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Wave JT - LED Chaser with Joule Thief 



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Wave JT - LED Chaser with Joule 
Thief 

Written By: Akimitsu Sadoi 



TOOLS: 


PARTS: 


Solderina iron (1) 


• Solder m 


Wire cutters (1) 


Wave JT kit (1) 



SUMMARY 

I love LED chasers. A bunch of LEDs neatly turning on and off on a precise timing - lights 
running one way, then the other way... It's relaxing, soothing, and hypnotic. 

There are so many LED chaser/scanner/sequencer circuits out there; some are made with 
discrete transistors, some based on logic ICs, and more and more others are using 
microcontrollers. 

There is one thing in common with all of the LED chaser circuits you find on the net - none of 
them can operate with just one alkaline battery! 

Most of us know that LEDs need at least 2.2V or so to light. Blue and white LEDs require 
even higher voltage, typically 3.2V. So obviously you can't use just one AA battery to 
operate an LED chaser. But we all know that there is the Joule Thief that boosts voltage high 
enough to light any LEDs. Why not use that to operate an LED chaser? 
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Wave JT - LED Chaser with Joule Thief 



Step 1 — Features 




• Wave JT is not only powered by a single AA battery, but it's feature rich. 

• Compact & streamlined design. 

• Uses only one AA battery (or any 1 .5V battery you can hook up to). 

• Works well with rechargeables (NiMH or NiCd) too. 

• Eight LEDs, each with its own 256 level brightness control. 

• Energy efficient - works even with a run-down battery, down to 0.6V (0.8V to startup). 



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Wave JT - LED Chaser with Joule Thief 



Step 2 — Circuit Schematics 




• The power supply (voltage booster) 
part of schematic shows somewhat 
typical Joule Thief circuit, plus a 
few extra parts. 

• D1 (Schottky diode) and C2 form a 
rectifier to create DC voltage out of 
the Joule Thief. Zener diode D2 is 
added to "clamp" or limit the 
voltage at 5. 1 V to prevent 
damaging the microcontroller 
(maximum voltage this chip can 
withstand is 6V). 

• Without the Zener diode there, the 
output voltage from the boost 
circuit can go over 6V when no 
LEDs are lit. 



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Wave JT - LED Chaser with Joule Thief 



Step 3 — Parts 








• Here are the parts. 

• LEDs should be of "super 
bright" variety. Standard 
LEDs are not bright enough for this 
circuit. Either 3mm or 5mm sizes 
can be used, however the PCB is 
somewhat optimized with 3mm 
LEDs. 5mm LEDs hang off the 
edge of the PCB a slight bit. Make 
sure to use the same LEDs for all 
eight of them. (Of course you can 
experiment mix & matching if you 
like.. 

• Parts list is included in the 
schematic PDF. 







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Wave JT - LED Chaser with Joule Thief 



Step 4 — Assembly 




• The assembly is very straightforward. Insert the parts into the PCB, and solder them. Start 
with lower profile components and move on to larger, taller ones. 

• Transistors, diodes, electrolytic capacitor and LEDs have polarities, so make sure to 
insert them in the correct orientation. Battery holders need a bit of force to snap into the 
holes. They attach from the back side of PCB as you can see in the picture. 

• Once everything is soldered in place, double check the part placement, orientation and 
solder joints for shorts and bad (cold) connections. 



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Wave JT - LED Chaser with Joule Thief 



Step 5 — Programming the Microcontroller (PIC) 




• Download the firmware HEX file here . 

• Insert 5-pin header to PICKit 2/3 or other PIC programmer, and stick the other end into the 
back of Wave JT PCB. The 5 holes that you use are marked ICSP, with an arrow pointing 
to the MCLR pin. 

• Set the programmer to supply V DD of 4.9V and program the PIC. 

Step 6 — Have fun! 




More detailed info available at Instructables and The LED Artist . 



Wave JT is fun! 

This document was last generated on 2012-11-01 09:14:15 PM. 



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